Microbial 'cheaters' help scientists ID 'soc...( HOUSTON Feb. 13 2008 -- The first ge...),Health

HOUSTON, Feb. 13, 2008 -- The first genome-wide search for genes governing social behavior has found that even the simplest social creatures -- the amoebae Dictyostelium discoideum -- have more than 100 genes that help regulate their cooperative behavior.

The study by scientists at Rice University and Baylor College of Medicine (BCM) was published online this week by the journal Nature. It marks one of the first large-scale attempts to combine evolutionary biology with genomics in a systematic search for genes tied to social behavior.

"This pool of genes is going to allow us to understand the genetic architecture of social behavior," said co-author Joan Strassmann, Rice's Harry C. and Olga K. Wiess Professor of Ecology and Evolutionary Biology.

Though little understood, social cooperation among microbes causes major medical and industrial problems. Medically, cooperation underlies conditions as mundane as tooth decay to more serious conditions like chronic infections associated with medical implants. Industrially, slimy colonies of bacteria also foul filters at water treatment plants and other facilities, causing millions of dollars of damage each year.

Rice and BCM's genome-wide investigation took five years and required the detailed study of some 10,000 randomly mutated strains of D. discoideum. "The basic idea was to knock out genes at random and put each mutant through 10 rounds germination, growth and development to identify mutations that led to cheating," Strassmann said.

Cheating mutations were found in more than 100 genes. Since there are advantages to be gained from cheating, Strassmann said the real mystery, from an evolutionary point of view, is how species like D. discoideum manage to keep cheaters from out-producing and eliminating cooperation altogether.

"This is just the beginning," said co-author Adam Kuspa, BCM's S. J. Wakil Chair of Biochemistry and Molecular Biology. "Now we need to defin
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